We are characterizing the filament packing in dense actin granules. F-actin is the major component of cytoskeleton of every mammalian cell. It is a semiflexible biopolymer of 8-10 nm in diameter and has a persistence length of a few microns. We have observed in vitro granules of F-actin, embedded in a fluid like background of concentrated F-actin. Phase contrast microsocpy shows these stable granules of densely paced F-actin to be of various sizes but of the well defined "American football" shape. Low-angle X-ray diffraction through the actin gels containing numerous, randomly oriented granules shows a clear ring corresponding to a basic spacing of 12 to 16 nm. Such a spacing corresponds to the packing of F-actin within the dense granules with interfilament separation less the the filament diameter, but the actual filament packing awaits direct visualization by electron microscopy. We plan to visualize the organization of actin in the granules using high resolution cryoSEM.